Underground storage of fluids in clay beds



May 9, 1961 c. F. TEICHMANN ETAL 2,983,103

UNDERGROUND STORAGE OF FLUIDS IN CLAY BEDS 7 P lnu l Filed Jan. 17, 1957IN V EN TORS CHARLES E 721/0 HMA NN A LLJEN D. GA 29/50 A! BY ATTORNEYPatented May 9, 1961 United States Patent Ofiice UNDERGROUND STORAGE OFFLUIDS IN CLAY BEDS Charles F. Teichmann, Crestwood, N.Y., and Allen D.

Garrison, La Jolla, Calif., assignors to Texaco DevelopglelllatCorporation, New York, N.Y., a corporation of e ware Filed Jan. 17,1957, Ser. No. 634,687

1 Claim. (Cl. 61-5) The present invention relates to the storage offluids, such as liquefied petroleum gases, in underground storagecavities formed in clay beds beneath the surface of the earth.

Such fluids as liquefied petroleum gases have been stored successfullywithin tremendous cavities formed in salt formations hundreds of feetbelow the surface of the earth. Storage in salt cavities has provenquite successful but, unfortunately, underground salt formationssuitable for this purpose are not available at every location wherestorage space is needed. It is well known that large underground clayformations are located in numerous places where no salt formationsexist, but up to the present time there has been no known way forutilizing such clay formations to store fluids.

In accordance with the present invention we have found that a largeunderground storage cavity can be formed at the bottom of a well withina clay formation hundreds at feet below the surface of the earth byflowing into contact with such a clay body a deflocculant liquid whichdeflocculates the clay and forms a clay-laden liquid, which is thenremoved from the clay body to form a large cavity. While water alone isa material removing liquid which has some deflocculating efiect uponclay, we prefer to employ a water solution of one or more chemicalswhich have a more pronounced deflocculating effect, for example, themolecularly dehydrated phosphates.

After the cavity has been enlarged sufliciently it is advantageous totreat its walls to reduce their premea'bility, and to prevent furtherdeflocculation during operation for storage purposes. Permeability canbe decreased by treating the walls of the cavity with a material such assodium silicate in water solution. While the sodium silicate can beemployed alone in water solution, it is advantageous to react thedeposited sodium silicate with a material which causes silicic acid orsilica to precipitate from the sodium silicate solution within the poresof the clay wall. Another procedure forreducing permeability is to coatthe walls with a polymerized plastic material such as rubber.

Continued deflocculation' of the clay walls of the cavity can be avoidedafter its completion by treating the walls with a water solutioncontaining a fiocculating agent, such as one or more salts from thegroup consisting of sodium and potassium thiocyanates, chlorates,iodides, nitrates, bromides, chromates, and chlorides. These agents canbe employed in a separate solution or in-the sodium silicate solutionpreviously mentioned.

In the drawing:

Fig. 1 is a schematic vertical sectional view of novel apparatus forcreating a storage cavity in a bed of clay by the principles of theinvention; and

- Fig. 2 is a cross-sectional view taken along the line 2-2 in Fig. 1.

More in detail in accordance with the invention, the first step afterlocating an underground clay bed of sufficient thickness is to drill adeep hole or well 11 from the surface of the earth 13 down throughintervening overburden into the clay formation 15. The top portion ofthe hole 11 preferably is cased at 17 to prevent the caving ofoverburden as the hole progresses. The bottom portion of the holedesirably is under-reamed to increase its diameter, as at 18, thusexpediting formation of the final cavity.

After completion of the hole 11 a long central pipe 19 is inserted to apoint a few inches from the bottom of the-hole for the removal ofclay-laden liquid to the surface 13.

Surrounding the central pipe 19 in spaced relation thereto is a secondpipe 21 which also extends down from the surface 13 into the hole 11,but terminates a substantial distance above the bottom of the centralpipe 19 for the injection of deflocculant liquid into the hole.

Packing glands 23 and 25 are disposed in the annulus 29 between pipes 19and 21 to prevent leakage of liquid while permitting the outside pipe 21to be moved lengthwise along the central pipe 19 to enlarge the holealong its full length.

Deflocculant liquid is pumped through a conduit 27 down through theannulus 29 between the two pipes and is then discharged into the hole.11 through a plurality of circumferentially spaced discharge ports 31above the gland 25. The washing action of the deflocculant liquid isenhanced by discharging it through the ports 31 as jets with such a highvelocity that they impinge against the side walls of the hole and washthe deflocculated clay detritus down to the bottom where the clay-ladenliquid 34 enters the central pipe 19 and is raised to the surface of theearth there to be discharged through a pipe 32 into'a screen 33 whichremoves much of the clay, and thence into a slush pit 35 in which theremaining clay settles. The washing action is accentuated by soconstructing the ports 31 that they extend generally tangentially at anangle to the pipe radius, as in Fig. 2, and thus discharge the liquidjets so that they swirl around the wall of the hole.

Pipe 21 can be moved lengthwise of the hole to extend the hole diameterthe full length of the desired cavity. Preferably the movement at thetop should be such as to form a conical ceiling 36 on the final cavity39 to prevent caving of the ceiling.

While Water alone has some deflocculating effect on clay, it ispreferred to incorporate in the water one or more chemical compoundswhich increase the deflocculating effect and thus increase the speed ofoperation.

Among such chemical compounds are the alkali and alkaline earth metalpolyphosphates, such as sodium or potassium tetraphosphate andtriphosphate. The deflocculating effect is aided by such materials evenwhen pres ent in very small amounts, but the effect increasesprogressively as the amount increases up to an optimum. A suitabledeflocculant liquid may contain between .001 and 0.50 percent of one ormore of the above compounds.

The clay-laden deflocculant liquid 34 can be removed through the centralpipe 19 in any desired way, as by employing a suction pump or byoperation with the cavity full of liquid under a hydrostatic pressurehead. We prefer, however, to maintain the level of the liquid in thehole at a point some distance below the ports 31 by maintaining a gasunder pressure above the liquid, thus making it possible .for'the highvelocity jets from ports 31 to impinge directlyagainst the side walls ofthe hole and exert the maximum Washing effect. Any suitable gas such asnatural gas, air, or carbon dioxide, can be employed, eitherindependently or by introducing it from a conduit 37 into the annulus 29to flow down into the hole along with the deflocculant liquid. Aconventional pressure regulator 38 maintains a constant gas pressure inthe hole.

Since the deflocculant liquid containing polyphosphates or otherdeflocculating chemicals is quite valuable, recir- 3 culation should beemployed, as by pumping used liquid from the slush pit 35 back into theannulus 29. Make-up liquid can be added as needed.

It may be found insome clays that the deflocculant liquid acts sorapidly upon the clay wall of the hole that the proportion ofdeflocculated clay in the liquid pool 34 becomes too large to handleeffectively. When such a situation arises it is desirable to retarddefiocculation temporarily by injecting into the hole through theannulus 29 a water solution containing a flocculating material such as.sodium or potassium chloride or the other materials mentionedpreviously herein. After a short time the flow of deflocculating liquidcan be resumed. This alternate action of deflocculating and fiocculatingliquids can be employed as often asnecessary to maintain the steadyprogress of hole enlargement.

After the hole 11 has been enlarged to the desired diameter over thedesired length to form a storage cavity 39, the clay Walls of the cavityshould be treated to assure impermeability, thus to prevent the leakageof liquefied petroleum gases or other liquids which are to be stored.This can be done by impregnating the wall of the hole with a sodiumsilicate solution to fill up the pores. For example, a water solutioncontaining to 20 percent by volume of a low alkali sodium silicate inwhich the molecular ratio of silica to sodium oxide falls within'therange of from 3.9:1 to 1.5 :1 can be introduced into the storage cavityto fill the latter, or can be applied to the walls by spraying it fromthe ports '31. If the sodium silicate treatment alone is not completelysatisfactory, it can be followed by treatment with a solution of amultivalent salt such as calcium or aluminum chloride or a dilute acidsolution such as dilute sodium chloride or hydrochloric acid, toprecipitate silicic acid or silica.

Another procedure which can be used successfully is to spray such asodium silicate solution on the walls of the storage cavity throughports 31 while maintaining within the storage cavity a large volume of agas containing a sutficient quantity of carbon dioxide to react with thedeposited sodium silicate and precipitate silicic acid. Such a gas canbe introduced from conduit 37 before or after the silicate solution.

Not only should the walls of the storage cavity be rendered asimpermeable as possible, but theremust also be assurance that furtherdefloccul-ation will not occur when the cavity is later operated for thestorage of fluids. This can be accomplished by applying to the walls ofthe storage cavity 39 a solution of a flocculating chemical compoundsuch as sodium'or potassium'chlorides, or any other salt selected fromthe group consisting of the sodium and potassium thiocyanates,chlorates, iodides, nitrates, bromides, chromates, and chlorides. Whileeven minor quantities of these salts inhibit deflocculation, it isdesirable to maintain the salt content of the solution within the rangeof from 20 percent by weight up to the saturation value of the dissolvedcomponent. The salt can be applied as a separate solution or can beincorporated in the sodium silicate solution previously mentioned.

After the storage cavity 39 has been completed as described above, itcan be immediately used for the storage of a fluid such as liquefiedpetroleum gas. The cavity can be filled with a suitable control liquidsuch as a water solution and the liquefied petroleum gas then pumpeddown through the annulus 29 to displace solution up through the centralpipe 19. When gas later is to be withdrawn from the storage cavity,solution is pumped down through the central pipe 19 and displaces gas upthrough the annulus 29. In order to maintain the walls of the storagecavity in a compact and impermeable condition it is advantageous to useas the control liquid a water solution of sodium silicate with orwithout a flocculant salt of the type described previously herein.

The method of storing liquefied petroleum gases described above also canbe used "for storing many liquids, as well as gases, which do notadversely affect the walls of the clay cavity. For example natural gasand butane can both be stored as liquids or gases. Also, gasoline andother normally liquid. petroleum hydrocarbons can be pumped from thesurface of the earth down into such a cavity and stored successfully.

An important advantage of this method of storage is that little if'anyof the stored-fluid is lost due to leakage or evaporation. This is inlarge part due to the formation of the cavity by washing it out with awater solution, followed by treating the walls to seal them. Any

' naturally existing pores, fissures or other natural inhomo- 'geneitiesare filled, covered over-and sealed by clay and the sealing chemicals.

This application is a continuation-in-part of application Ser. No.305,964, filed August 23, 1952, now US. Patent 2,803,432, granted August20, 1957;

"Obviously, many modifications and variations of the invention, ashereinbefore set forth, may be made without departing from the spiritand scope thereof, and therefore only such limitations should be imposedas are indicated in the appended claim.

We claim:

A method of operating an underground fluid storage reservoir comprisinga cavity in a natural underground clay body beneath the surface of theearth, said method comprising providing in said reservoir a pool of awater solution containing at least one salt selected from the groupconsisting of sodium and potassium thiocyanates, chlorates, iodides,nitrates, bromides, chromates and chlorides to prevent defiocculation ofsaid clay and keep the walls of said reservoir stable and impermeable,feeding a stream of the fluid to be stored into said reservoirunder apressure sufficient to displace water solution from said pool to thesurface of the earth, and subsequently recovering the fluidso stored byfeeding a stream of said water solution back into said reservoir under apressure sufficient to displace stored fluid from said reservoir to thesurface of the earth, whereby the walls of said reservoir are keptstable and impermeable.

References Cited in the me of this patent UNITED STATES PATENTS Re.24,318 Pattinson May 14, 1957 671,429 Bacon Apr. 9, .1901 1,421,706Mills Iuly'4, 1922 1,460,788 Carman July 3, 1923 2,198,120 Lerch Apr.23, 1940 2,200,710 Bentetal. May 14,1940 2,239,647 Garrison Apr. 22,1941 2,365,039 Andersen Dec. 12, 1944 2,413,213 -Nefi Dec. 24, .19462,459,227 Kerr Jan. 18, 1949 2,720,381 Quick Oct. 11, 1955 2,803,114Hudson Aug. 20, 1957 2,803,432 Teichmann Aug. 20, 1957 FOREIGN PATENTS738,917 'Gre'at Britain 1955 OTHER REFERENCES Clays" by Heinrich Ries,3rd ed; 1927; page 183.

